Devices having a retractable sheath associated with a catheter are used to treat a variety of conditions using endoluminal methods instead of open surgical procedures. For example, angioplasty and stent implantation procedures are often used to treat atherosclerotic disease or other occlusive conditions in blood vessels, such as the coronary and carotid arteries. During angioplasty, a catheter having an uninflated balloon on its distal end is percutaneously introduced into a patient's vasculature and advanced to a target treatment location, such as a stenosis within a blood vessel. Once the balloon is properly placed across the stenosis, the balloon is inflated to enlarge the lumen or vessel at the location of the stenosis. The balloon is then deflated, the inflation/deflation procedure may be repeated, and then the catheter is withdrawn from the patient's body.
To help prevent arterial closure, repair dissection, or prevent subsequent restenosis, a physician can implant an intravascular prosthesis, or a stent, for maintaining vascular patency inside the artery at the lesion. The stent may either be a self-expanding stent or a balloon expandable stent. For the latter type, the stent is often delivered on a balloon and the balloon is used to the expand the stent. Self-expanding stents may be made of shape memory materials such as nitinol or constructed of conventional metals but of a design which exhibits self expansion characteristics.
In certain known stent delivery catheters, a stent and an optional balloon are positioned at the distal end of the catheter, around a core lumen. The stent and balloon are held down and covered by a sheath or sleeve. When the distal portion is in its desired location of the targeted vessel, the sheath or sleeve is retracted to expose the stent. After the sheath is removed, the stent is free to self-expand or be expanded with a balloon.
For control of the sheath during deployment, several procedures have been proposed. The user may simply pull the proximal end of the sheath while holding the catheter in a fixed position. This, however, may not easily provide precise control of the retraction of the sheath.
To provide improved control, handle devices have been proposed which include a wheel and screw mechanism. A wheel extending around the circumference of the handle is coupled to a screw mechanism engaging the sheath and the catheter. As the wheel is rotated about the longitudinal axis of the handle, the screw mechanism moves the sheath axially with respect to the catheter.
With such devices, however, it may be difficult to remember which direction, i.e., clockwise or counterclockwise, is appropriate either to retract or advance the sheath with respect to the catheter. This may be particularly important when immediate action is necessary because of a complication during a procedure. In addition, these screw-type devices may be complicated, including many parts which may be difficult to assemble and/or expensive to make.
Another device has provided large handles to improve the ease and accuracy with which a stent can be delivered. However, as the French size of the device is reduced, the moving parts of the interior may not provide support for the catheter during the retraction procedure.
Accordingly, there is a need for an improved, intuitive, simple and safe device for controlling catheter-sheath systems.